Television and like apparatus



May 26, 1931. J BAlRD 1,807,465

TELEVISION AND LIKE APPARATUS Filed Oct. 7, 1929 Fatentecl May 26, 1931UNITED STATES PATENT OFFICE JOHN LOGIE BAIRD, OF LONDON, ENGLAND,ASSIGNOR TO TELEVISION LIMITED, OF LONDON, ENGLAND, A BRITISH COMPANYTELEVISION AND LIKE APPARATUS Application filed October 7, 1929, SerialNo. 397,985, and in Great Britain October 12, 1928.

This invention is for improvements in or relating to television and likeapparatus and has for its object to' provide improvements in connectionwith the means employed for 5 exploring an object, an image of which isto be transmitted. Our British patent specification No. 269,658describes a method whereby an object, an image of which is to betransmitted, may be explored by traversing over 1 it a spot of light ofhigh intensity.

According to this invention, in television or like apparatus, means areprovided for exploring an object (an image of which is to betransmitted) in separate bands or zones 15 by a plurality of lightspots, one appropriated to each zone, and a plurality of light-sensitivecells of which one is allocated to each zone and each is activated bylight reflected from the zone to which it is allocated.

Each light sensitive cell may be screened to prevent light from reachingit except from its appropriate zone or band.

Convenient forms of apparatus according to this invention will now bedescribed by way 2 of example, with reference to the accompanyingdiagrammatic drawings, in which:

Figure 1 represents a television apparatus according to this invention,for transmitting an image of an opaque object.

Figure 2 represents a modified form of television apparatus according tothis invention for transmitting an image of a translucent object suchas, for instance, of a kinematographic film.

Figure 3 represents a convenient form of shutter for use in televisionapparatus according to this invention.

Like references denote like parts throughout the drawings.

Light from a source is projected in a parallel beam by a lens 11 onto anexploring device 12. The exploring device is provided with threeconcentric spirals of holes 13 0 through which the light passes. Aconverging lens 14 focusses the light which passes through the holes 13of the exploring device on the object 15. When the exploring devicerotates, the object 15 is explored by three spots of light. The spiralsof holes 13 are so arranged that the spots of light traverse adjacentzones of the object.

Referring to Figure 1, near to the object, but out of the field swept bythe light spots, are arranged three light-sensitive cells or groups ofcells 16, 17 18. Each cell is screened in by partitions 19 of opaquemate rial so that it can receive light rays reflected only from itsappropriate zone of the object 13.

The light-sensitive cells may be disposed above or below the level ofthe object or alternatively, there may be two light sensitive cells foreach zone of the object, one above the level of the object and the otherbelow it.

With the arrangement shown diagrammatically in Figure 2, thelight-sensitive cells 16, 17, 18 are placed behind the object 15, whichis of translucent material. Only two screens 19 are necessary, and thelight-sensitive cells 16, 17, 18 may have each an active area comparablewith that of its zone, in which case they may be situated closely behindthe object 15.

In the apparatus described above, three light-sensitive cells or groupsof cells and three zones of the object are employed, but it falls withinthe scope of this invention to provide any number of such zones togetherwith an equal number of light-sensitive cells or groups of cells.

In a television system in which the above described apparatus isemployed, there may either be one channel of communication for eachlight-sensitive cell (e. g. three systems of conductors or threedifferent wave-lengths) or there may be one common channel ofcommunication.

If one common channel of communication is to be used, there may beemployed a commutator or switching device, which connects thelight-sensitive cells in turn to the amplifying and transmitting systemor alternatively there may be employed a shutter of the type describedin our co-pending British patent application No. 23,582 of 1929. Such ashutter, suitable for use in conjunction with apparatus described above,is illustrated in Fig ure 3. It consists of a circular disc 20 providedwith as many slots 21 as there are zones of the object 15. (In thisinstance, three.) The discs may conveniently be mounted on the axle 22of the exploring device and driven thereby through a gear reduction of3:1.

This invention is also applicable for use in the transmission bytelevision, of images of groups of separate objects. Thus the appara tusdescribed above might be conveniently employed in the transmission ofimages of three persons. The spirals of holes 13 in the exploring device12 might be slightly spaced apart so that the gaps between the personswould not be explored or transmitted.

I claim- A scanning device for use in television apparatus comprising asource of light, a rotating screen interposed between said source oflight and an object to be scanned, said screen having a plurality ofseriesof spirally arranged apertures therein, the apertures in thedifierent series beingspaced radially of said screen whereby light raysWill be passed from said source across different sections of the objectsimultaneously, and a plurality of light sensitive devices eachpositioned to receive light from one of said sections of the objectonly.

In testimony whereof I affix my signature.

JOHN LOGIE BAIRD.

